A stellar orange dwarf has a 90% chance of passing through the outer reaches of our solar system no earlier than a quarter of a million years from now. Sure, that's a long way off, but this unwelcome guest could perturb the Oort cloud, flinging dangerous comets towards Earth.

Top image: Comet Siding Spring coming in after spending millions of years in the Oort Cloud. Incoming stars have the potential to hurl swarms of similar comets towards the inner solar system. Image credit: NASA/JPL-Caltech/UCLA.

After analyzing the computer-simulated orbits of more than 50,000 nearby stars, European astrophysicist Coryn Bailer-Jones is predicting that 14 stars could come within one parsec (~3 light-years) over the next few million years, but there are at least two we should be wary of. As New Scientistreports:

The star that is set to come closest is called Hip 85605, and has a 90 per cent chance of reaching between 0.13 and 0.65 light years away from us in the next quarter to half a million years – although its current position data isn't entirely clear so the estimate may be wrong. The next closest is GL 710, which has a 90 per cent chance of reaching 0.32 to 1.44 light years in the next 1.3 million years.

Either one would be close enough to influence the Oort cloud, which extends from 0.0065 to around 1.63 light years from the sun. "I think we can safely predict that comet orbits would indeed be disrupted by the closest encounters," says Bailer-Jones. He is now working on a follow-up study to determine the probability of Earth being hit by a comet as the result of a star passing by.

Bailer-Jones' study is set to appear in an upcoming issue of Astronomy & Astrophysics, but you can check it out here at the arXiv pre-print archive. Also, be sure to check out Bruce Dorminey's excellent coverage of the paper.